Eucalyptus, the third, so-called ugly sister of open source cloud computing projects, gets less attention than OpenStack and CloudStack, but remains in contention to provide the software for the enterprise "private" cloud.

The "ugly sisters" were so named by a less than diplomatic VMware executive, Mathew Lodge, VP of cloud strategies, in an April blog on the VMware site. Eucalyptus was around before OpenStack and CloudWatch, making it the elder of the three. In the eyes of Eucalyptus CTO Rich Wolski, the company will yet emerge as the belle of the ball.

Wolski is the University of California at Santa Barbara computer science professor who started a project five years ago to build open source APIs. In 2007, there weren't many models to choose from. There was Amazon's EC2 and not much else. So Wolski and his students created open source alternative APIs for the AWS S3 and EC2 compute and a few other basic AWS services.

That move brought neither approval nor disapproval from Amazon Web Services, just a brooding, five-year silence until last March when Eucalyptus became the only private cloud software vendor to enter into a partnership with Amazon. By creating an open source alternative, Eucalyptus was helping customers build out their own clouds in a way that Amazon couldn't, while still building in Amazon compatibility. Amazon agreed to help Eucalyptus achieve compatibility and continues to do that.

"This agreement is going to accelerate our roadmap and help us maintain our compatibility with AWS," said CEO Marten Mickos at the time. And a total of $60 million in venture capital lined up behind the company by mid-April.

The firm has been criticized for focusing so early on Amazon APIs. But Wolski said he has read the code and found it incorporates some principles of API programming that are good for a major e-commerce site such as Amazon.com and also good for implementing cloud computing. For example, a cloud API doesn't allow a user to attempt to assemble many catalog items at once, then tell the e-commerce system to dump them all into a shopping cart. Instead, it gets the user to execute discrete steps, such as selecting and adding one item at a time to the cart. "It's important that each step succeed or fail in a way that unambiguous," said Wolski, and Amazon's cloud APIs require that as well.

Because the APIs are compatible, Eucalyptus users may build private cloud applications that call on in-house compute and storage services; they also can be run without change in the Amazon cloud. As a result, the Eucalyptus customer base is a heavy user of the hybrid cloud pattern, where an in-house application that is overtaxed by traffic and can spin up additional instances in the public cloud to absorb the load. About "90% of our customers have a hybrid computing plan; 30% to 40% are using the two together already," Wolski said.

That figure may go up in the second week of December when release 3.2 of the Eucalyptus code becomes available. Like VMware and the OpenStack project, Eucalyptus has been adding virtualized networking to its approach. It's implementing virtual nets by making use of the open source code Open vSwitch, now part of the Linux kernel, to manage communications between virtual machines on a shared host or between a virtual machine and the external network.

Wolski said he has read the code that Nicira produces and "can see why VMware is excited about Nicira," which it acquired for $1.26 billion last July. But Nicira's approach to virtualizing the network isn't the only way to accomplish that goal. Eucalyptus is building its own network virtualization layer that can use open source code Open vSwitches to set up virtual nets for VMs. Each virtual network will have individual characteristics as required, such as enhanced security or ultra-high performance, determined either by pre-programmed rules or a network administrator accessing the vSwitch from a network management console.

Eucalyptus' approach is simpler and easier to implement than Nicira's Network Virtualization Platform, which builds a network controller that can program vSwitches embedded in the network. Eucalyptus will use the vSwitch in the Linux kernel "to control the virtual network the same way Nicira does" without requiring all the added parts and create virtual local area nets as needed by each VM.

How much network virtualization will be ready for the next release versus waiting for a future release, Wolski wouldn't say at this point. But he said no single open source code project was going to be the only purveyor of virtualized nets deployed with virtual machines. OpenStack developers are addressing virtual networking through its Quantum Project, led by a former Nicira designer and development team leader, Dan Wendlandt.

Eucalyptus is positioned as a high availability, simple-to-implement set of cloud software, Wolski said. The 3.2 release will include a user interface that simplifies set up of a Eucalyptus private cloud. It will furnish more diagnostics on the cloud's operation and store the data in an added data warehouse, where it can perform analytics on them.

As compute, storage and networking become virtualized, the enterprise data center can begin to more closely resemble the large cloud suppliers and how they operate. When business users need a server, "the resource allocation burden is put on the cloud itself" in a Eucalyptus cloud. That frees up human administrators in the IT department.